How do I calculate bicycle tire pressure?

Enter your total system weight (rider + bike + gear), tire width, rim type, and terrain. VeloPSI calculates separate front and rear PSI recommendations using empirically validated models calibrated against professional cycling data.

How does temperature affect bike tire pressure?

Temperature changes cause tire pressure to fluctuate approximately 1.5 PSI per 10°F. Using Gay-Lussac's Law, VeloPSI calculates what pressure to inflate to indoors so that your tires reach the correct pressure at your riding temperature.

What PSI should I run for tubeless tires?

Tubeless tires typically run 5–15% lower pressure than equivalent tubed setups at the same load. VeloPSI applies this discount automatically when you select a tubeless rim type.

What is the maximum PSI for hookless rims?

ETRTO 2020 standard sets hookless rim maximum pressure at 72.5 PSI for 25–29mm tires, decreasing to 43.5 PSI for 45–54mm tires. VeloPSI enforces these limits automatically and warns when you approach them.

Should front and rear tire pressure be different?

Yes. Rear tires carry more weight and need higher pressure. VeloPSI calculates front and rear independently based on your weight distribution, typically resulting in 10–20% higher rear pressure for road bikes.

Bicycle Tire Pressure Calculator

Name: VeloPSI
Author: VeloPSI

Rider + Bike + Gear

Combined total — rider, bike, kit, and any cargo

Width unit

Front Width

Rear Width

Wheel Size

Rim Type

Tire Casing

Reinforced casings support lower pressures by providing structural protection

Front Fork

Rigid: lower front pressure (tire does all suspension). Suspension: higher front + harder rear (fork handles impacts). MTB widths only.

Primary Surface

Secondary Surface

Inflation Temp

°F

Ride Temp

°F

Gay-Lussac absolute pressure correction · fills both fields with current outdoor temp

Default: auto from tire width. Override for cargo, bikepacking, tandems, or unusual setups.

Front 41%

Rear 59%

–

PSI / – bar

–

PSI / – bar

–

Save this setup →

Up to 5 bikes · stored on this device only

How VeloPSI calculates

A unified engine blends two empirically validated models based on tire width. Narrow widths use the Dave Adams power-law derived from Frank Berto's 15% tire-drop research. Wide MTB widths use a model calibrated against Wolf Tooth Components' calculator. The two blend continuously via sigmoid — road-dominant below ~35mm, equal blend at 44mm, MTB-dominant above ~50mm. No hard switch.

The math

Road: P = 153.6 × (Load / Width^1.5785) − 7.1685
MTB: P = 25.1 × Weight^0.60 / Width^0.80
Blend: sigmoid centered at 44mm · steepness 0.22
F/R split: 41/59 road → 47/53 MTB (width-dependent)

Road pressure and modern science

Modern empirical calculators (SILCA, Zipp/SRAM, Rene Herse) recommend significantly lower pressures than 1990s–2000s cycling culture. For a 60kg rider on 25mm tubeless, SILCA outputs ~57 PSI front — not the 80–95 PSI that was once common. Lower pressure reduces impedance losses on real roads, improves grip, and reduces fatigue. VeloPSI follows modern empirical data.

Hookless ETRTO limits

Width	Max PSI
≤ 24mm	79.7
25–29mm	72.5
30–34mm	65.2
35–39mm	58.0
40–44mm	50.7
45–54mm	43.5
≥ 55mm	36.2

Warning fires at 5 PSI below limit — hot pavement can add 5+ PSI above inflation pressure.

Fork suspension adjustment

On gravel and MTB widths (>35mm), fork type adjusts both front and rear. Rigid / traditional gravel: front −5% (tire does all suspension), rear +4% (no rear shock). Short-travel gravel fork (Lauf, Rudy, Fox AX): front +1%, rear +4%. Hardtail / XC fork: front +4%, rear +4% (rigid rear still absorbs all impacts). Full suspension trail/enduro: front +6%, rear unchanged (rear shock handles it). No effect on road widths. Percentage-based so adjustments scale correctly at any pressure.

Temperature

Uses absolute pressure Gay-Lussac: (P + 14.7) × (T_inflation_K / T_ride_K) − 14.7, where temperatures are in Kelvin. Approximately 1.5 PSI per 10°F. Tap “Use my location” to auto-fill both fields with current outdoor temperature via Open-Meteo. Location is used only for this fetch and immediately discarded.

Your data

All calculations run locally in your browser. Nothing is sent to any server. Bike profiles use localStorage on this device only. Location is fetched once for temperature and never stored.

Disclaimer

VeloPSI provides tire pressure recommendations as a starting guide only. Always verify your tire's maximum pressure rating printed on the sidewall and your rim manufacturer's specifications. Ride conditions, rider skill, and equipment vary — always use your own judgment. The rider is solely responsible for all pressure decisions. VeloPSI and its authors accept no liability for any outcome resulting from use of these recommendations.

Sources

Dave Adams / Frank Berto 15% tire-drop · Wolf Tooth Components calibration · Jan Heine / Bicycle Quarterly · SILCA impedance methodology · Vittoria Labs · ETRTO 2020 hookless standard · Gay-Lussac's Law · Open-Meteo weather API